Persistent edge state of end user devices at cache nodes

ABSTRACT

Systems, methods, apparatuses, and software for caching tracking elements of network content are provided herein. In one example, a method of operating a cache node of a content delivery network that caches content for delivery to end user devices is provided. The method includes receiving content requests from an end user device for content cached by the cache node and responsively providing the content for delivery to the end user device, processing the content requests to determine a edge state that corresponds to the end user device, transferring information related to the edge state for delivery to at least one other cache node of the content delivery network for handling of content requests received at the at least one other cache node.

TECHNICAL FIELD

Aspects of the disclosure are related to the field of packetcommunication networks and delivery of content from content servers toend user devices.

TECHNICAL BACKGROUND

Network-provided content, such as Internet web pages or media contentsuch as video, pictures, music, and the like, are typically served toend users via networked computer systems. End user requests for thenetwork content are processed and the content is responsively providedover various network links. These networked computer systems can includeorigin or hosting servers which originally host network content, such asweb servers for hosting a news website. However, these computer systemsof individual content origins or hosts can become overloaded and slowdue to frequent requests of content by end users.

Content delivery networks have been developed which add a layer ofcaching between original servers of the content providers and the endusers. The content delivery networks typically have one or more contentnodes distributed across a large geographic region to provide faster andlower latency access to the content for the end users. When end usersrequest content, such as a web page, which is handled through a contentnode, the content node is configured to respond to the end user requestsinstead of the origin servers. In this manner, a content node can act asa proxy or cache for the origin servers. Content of the origin serverscan be cached into the content nodes, and can be requested via thecontent nodes from origin servers when the content has not yet beencached.

Additionally, network activities, such as browsing habits, of end userdevices can be monitored using various tracking elements. Networkcontent, such as web pages, can include tracking elements, such webbugs, beacons, or tracking pixels which are used to determine when usershave viewed various network content, such as in a web browserapplication. Various statistical data for the content browsingactivities of the end users can be monitored for web analytics, pagetagging, advertisement selection, among other activities. However, usertracking elements, such as cookies, are also difficult to manage becausethey are typically personal and user specific. These tracking elementsalso involve placing code, special content, or trackers on the localdevice through which the end user device browses content.

Overview

Systems, methods, apparatuses, and software for caching trackingelements of network content are provided herein. In one example, amethod of operating a cache node of a content delivery network thatcaches content for delivery to end user devices is provided. The methodincludes receiving content requests from an end user device for contentcached by the cache node and responsively providing the content fordelivery to the end user device, processing the content requests todetermine a edge state that corresponds to the end user device,transferring information related to the edge state for delivery to atleast one other cache node of the content delivery network for handlingof content requests received at the at least one other cache node.

In another example, a content delivery network is provided that includesa plurality of cache nodes that cache content for delivery to end userdevices. The content delivery network also includes a first cache nodeconfigured to receive first content requests from an end user device forcontent cached by the cache node and responsively provide the contentfor delivery to the end user device, process the first content requeststo determine a edge state that corresponds to the end user device, andtransfer information related to the edge state for delivery to at leasta second cache node of the content delivery network. The second cachenode is configured to receive second content requests and determine thatthe second content requests are associated with the end user devicebased at least on the information related to the edge state.

In another example, a method of operating a cache node of a contentdelivery network that caches content for delivery to end user devices isprovided. The method includes, in the cache node, receiving a contentrequest issued by an end user device corresponding to content cached bythe cache node, establishing edge state data for the end user devicebased at least on the content request and properties of the end userdevice, and persisting the edge state data for handling further contentrequests from the end user device.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the views. While multiple embodiments are described inconnection with these drawings, the disclosure is not limited to theembodiments disclosed herein. On the contrary, the intent is to coverall alternatives, modifications, and equivalents.

FIG. 1 illustrates a communication system.

FIG. 2 illustrates a method of operation of a content node.

FIG. 3 illustrates a communication system.

FIG. 4A illustrates a method of operation of a content delivery network.

FIG. 4B illustrates a method of operation of a content delivery network.

FIG. 5 illustrates a method of operation of a content delivery network.

FIG. 6 illustrates a content node.

DETAILED DESCRIPTION

Network content, such as web content, typically comprises text,hypertext markup language (HTML) pages, pictures, digital media content,video, audio, code, scripts, or other content viewable and rendered byan end user device in a browser or other specialized application.However, HTML requests are stateless and do not persist informationbetween requests of similar or different users. Various schemes havebeen developed to maintain state information between HTML requests,typically on a per-user basis. One such scheme is to use specializednetwork content which includes tracking elements, such as web bugs, webbeacons, tracking pixels, tags, images, or cookies, among other trackingelements. These tracking elements can be used to determine informationabout network content browsing activities of end user devices, for webanalytics, hit rate calculations, among others. However, these trackingelements involve placing code, special content, or trackers on the localuser device through which the end user browses content.

Content delivery networks can add a layer of caching between originservers of the content providers and the end users. The content deliverynetworks typically have one or more cache nodes distributed across alarge geographic region to provide faster and lower latency local accessto the content for the end users. When end users request content, suchas a web page, a selected cache node will respond to the content requestinstead of the associated origin server. Various techniques can beemployed to ensure the cache node responds to content requests insteadof the origin servers, such as associating web content of the originservers with network addresses of the cache nodes instead of networkaddresses of the origin servers using domain name system (DNS)registration and lookup procedures. Although cache nodes and originservers are shown as different nodes in the examples herein, it shouldbe understood that the origin servers and cache nodes can be included inone or more of the same nodes.

As a first example of maintaining state using cache nodes in a contentdelivery network, FIG. 1 is a system diagram illustrating communicationsystem 100. Communication system 100 includes cache nodes 110-111, oneor more end user devices 120, and origin server 130. Cache nodes 110-111and end user devices 120 can communicate over associated packet networks150-151, although further packet networks can be included. Cache nodes110-111 and origin server 130 communicate over network link 152.

In operation, cache nodes 110-111 cache content of at least originserver 130. This content can include web pages, media content, data,executable code, scripting content, among other types of contentdeliverable over packet networks 150-151. Cache nodes 110-111 delivercontent upon request to end user devices 120, or other end user devices,over associated ones of packet networks 150-151. By caching the contentof origin server 130 or other origin servers, cache nodes 110-111 canprovide faster access to this content to end user devices, such as enduser devices 120. In many examples, a plurality of cache nodes areincluded in a content delivery network (CDN) which provides cache nodesdistributed over a large geographic area for lower latency access tocontent normally provided by one or more origin servers. Cache nodes110-111 can also cache dynamic content, such as content generatedresponsive to activities of end user devices 120.

To provide various supplemental services to end user devices 120, suchas custom-tailored content, specific advertisement content, or othersupplemental content for end user devices, the content requestactivities of the end user devices can be tracked by at leastmaintaining state information in a cache node, such as edge state 140 inFIG. 1. Furthermore, the content request activities of end user devicescan be tracked in an anonymous or semi-anonymous manner to providevarious statistical information to allow origin servers or other contentproviders to determine traffic counts, web page request counts, usageinformation, traffic patterns, traffic sequences, hit rates,advertisement conversion rates, among other statistical and analyticsinformation associated with content requests of end user devices. Inaddition, cache nodes can execute per-user functions based on activitiesof end user devices, such as content requests, or based on stateinformation that is persisted in the cache node for end user devices,which can include edge state 140. These per-user functions are indicatedby element 141 in FIG. 1.

To further illustrate example operations of system 100, FIG. 2 isprovided. FIG. 2 is a flow diagram illustrating a method of operatingcache node 110. The operations of FIG. 2 are referenced belowparenthetically. In FIG. 2, cache node 110 receives (201) contentrequests from end user devices 120 for content cached by cache node 110and responsively provides the content for delivery to end user devices120. In FIG. 1, two example web pages are cached by cache node 110,namely web pages 160-161. These web pages can be originally hosted byorigin server 130, such as shown in FIG. 1, although separate originservers can be used. Cache node 110 can cache any of web pages 160-161in one or more storage media of cache node 110. The caching can beresponsive to end user requests for the associated web page content orpreemptive before end user requests. Cache node 110 can cache the webpages themselves, along with any content linked to or referenced by theweb pages. Web pages 160-161 can include any web content accessiblethrough a browser application or specialized application executed by enduser devices 120. For example, web pages 160-161 can include variouscode and scripts which link to media content, pictures, audio, text,objects, forms, data, or other network content. Web pages 160-161 caninclude hypertext markup language (HTML), Javascript, executable code,scripts, cascading style sheets (CSS), links, or extensible markuplanguage (XML), among other elements and content types.

Cache node 110 processes (202) the content requests to determine edgestate that corresponds to activity of end user devices 120. Typically,information regarding activity of an end user or end user device doesnot persist over more than one web page request or content request.However, in the examples herein, cache node 110 determines stateinformation associated with the content requests or with activity of enduser devices 120 and persists this edge state throughout many web pagerequests or other activity. In some examples, the edge state cancomprise an activity “fingerprint” determined on a per-user basis incache node 110. In other examples, the state can comprise activitycounters or statistical state information which spans the activities ofmany end user devices or content requests.

The edge state can be determined by processing content requests todetermine metrics 121 associated with at least the content requests ofend user device 120. Metrics 121 can be determined from the contentrequests, such as by processing information included in packets thatform the content requests or from other related handshaking, protocoloverhead information, packet headers, link properties, accompanyingquery parameters, or other information. For example, metrics 121 cancomprise a geographic location associated with end user device 120, anetwork address associated with the content requests, a network addressoriginating the content requests, a time/day of the content request,various information about the software environment of the end userdevice, a type of content browser application employed by end userdevice 120 to issue the content requests, a version of the contentbrowser application, operating system information of the end userdevice, and identities of at least one browser plug-in elementassociated with the content browser application. The network address cancomprise an Internet Protocol (IP) address, among other networkaddresses. In other examples, the network address can indicate anaddress range of which the network address of end user device 120 is amember. HTTP referrer information can be tracked as the edge state,where the HTTP referrer comprises an HTTP header field identifying anetwork address of a uniform resource identifier (URI) or uniformresource locator (URL) that linked to the content requested. TrackingHTTP referrer information as the edge state can provide an indication ofthe parent web page from which content is requested, such as responsiveto a hyperlink selected by an end user.

In this example, the edge state is persisted in at least cache node 110for identification of other activity as being related to one of end userdevices 120 or correlation of multiple content requests among many enduser devices. For example, cache node 110 determine that further contentrequests received at cache node 110 are associated with one end userdevice 120 based on at least edge state 140. Cache node 110 determinetracking activity of the same end user device 120 for further contentrequests received at cache node 110 based at least on edge state 140. Totrack or persist edge state 140 for end user device 120 or for any otherend user devices, cache node 110 can include one or more data structuresor databases.

In further examples, cache node 110 can determine that further contentrequests received by cache node 110 for content of a second web site areassociated with end user device 120 based on at least edge state 140,and identify browsing statistics for end user device 120 comprising aweb site browsing sequence for end user device 120 based at least on thecontent requests and the further content requests. The web sites or webpages can be associated with different content providers, such asdifferent origin servers instead of just origin server 130 in FIG. 1.Cache node 110 can identify web page request activity, such as web pagebrowsing activity of end user devices 120, which includes sequences ofbrowsing that indicate an order of web page requests or web sitesbrowsed, among other information. This information can be provided toorigin servers, content providers, or to analytics systems or trackingsystems which can identify supplemental content to provide to end userdevice 120, such as advertising content, or to further enhance contentof existing web sites. Cache node 110 can transfer browsing statisticsfor delivery to a content provider associated with at least one of afirst web site and a second web site.

Cache node 110 can execute per-user functions based on edge state 140,such as per-user functions 141. These per-user functions can includetracking functions as mentioned above. These per-user functions caninclude rate limiting of content requests or other related traffic on aper-user basis, statistical monitoring of users, URL shortening on aper-user or multi-user basis, accounting tracking, paywall tracking, orother per-user functions. Cache node 110 can determine when furthercontent requests received at cache node 110 are associated with a sameend user device as previous content requests based at least on an edgestate, and execute at least one per-user function at cache node 110responsive to the further content requests being associated with thesame end user device.

One example per-user function can include URL shortening at cache node110. URL shortening typically involves encoding or translating a nativeURL or natural URL into a shortened or abbreviated form for easier userby an end user. For example, a URL can include a domain name, servername, pathnames, and query parameters, among other information, and canbecome very long and cumbersome for an end user to use for linking,transferring, sharing, or other functions. A URL shortening feature cantranslate the URL for a website or webpage into a shortened version,such as a provided by a URL shortening service. However, these shortenedURLs are typically not persisted by a cache node nor cached by a cachenode.

Cache node 110 can receive a uniform resource locator (URL) shorteningrequest issued by an end user device to establish a shortened URL for anative URL corresponding to content cached by the cache node. Responsiveto the shortening request, cache node 110 determines a shortened URLcorresponding to the native URL, and indicates the shortened URL to theend user device. Moreover, cache node 110 can persist the shortened URLin an edge state for use by the end user device at a later time, or foruser by further end user devices that issue URL shortening requests forthe same native URL. A URL shortening service need not be involved inthe initial or further URL shortening requests issued by end userdevices, as correlations between shortened URLs and native URLs can beestablished by cache node 110 and persisted among more than one end userdevice. When the end user device issues a content request for theshortened URL, then cache node 110 can provide content to the end userdevice, where the content is cached by cache node 110. Thus, both thecontent and the shortened URL can be cached by cache node 110 for use bymore than one end user or end user device.

Cache node 110 transfers (203) edge state 140 for delivery to anothercache node of the content delivery network for handling of contentrequests received at the other content node. In this example, cache node110 transfers edge state 140 for delivery to cache node 111. Cache node111 can be located in a different geographic location than cache node110, such as when included in a content delivery network that spansseveral states, countries, or global regions. Further content requestsissued by end user devices 120 can be identified by cache node 111 andper-user functions can be executed by cache node 111 responsive to thosefurther content requests. Cache node 111 can advantageously be aware ofinformation of end user devices 120 using edge state 140 initiallyidentified by cache node 110 and transferred to cache node 111.Additions, changes, or alterations to edge state 140 can be establishedby cache node 111 and transferred for delivery to cache node 110, amongother cache nodes. Advantageously, information on end user devices asindicated by the edge state can be transferred across many differentcache nodes, which can span many different geographic regions.

Activity of end user devices can be tracked over the multiple cachenodes, which can identify activities of the end user devices based ongeographic movement, web page content requests, or other information.This activity can be tracked on a per-content basis, per-address basis,per-URL basis, per-country basis, per-region basis, per-user basis, orother distinctions. For example, when an end user device is malicious,and is performing an attack on content cached by cache node 110, theedge state for that end user device can be determined and transferred toanother cache node, such as cache node 111, which can identify when thatend user device attempts to attack content cached by cache node 111.Other tracking of non-malicious end user devices can be performed, suchas when an end user device is associated with a content subscription,and the cache nodes of a content delivery network can persistauthorization or authentication information for the end user deviceamong the various cache nodes to prevent unneeded traffic withauthorization or authentication servers when an end user device moves toanother location or establishes a network connection through a differentroute.

Furthermore, in URL shortening examples, once a first cache nodedetermines a shortened URL corresponding to a native URL, that shortenedURL can be transferred to other cache nodes which can then persist theshortened URL for use by other end user devices which issue URLshortening requests to those other cache nodes.

Returning to the elements of FIG. 1, cache nodes 110-111 can eachinclude communication interfaces, network interfaces, processingsystems, computer systems, microprocessors, storage systems, storagemedia, or some other processing devices or software systems, and can bedistributed among multiple devices. Examples of cache nodes 110-111 caneach include software such as an operating system, logs, databases,utilities, drivers, networking software, and other software stored on acomputer-readable medium.

End user devices 120 can each be a user device, subscriber equipment,customer equipment, access terminal, smartphone, personal digitalassistant (PDA), computer, tablet computing device, e-book, Internetappliance, media player, game console, smartwatch, or some other usercommunication apparatus, including combinations thereof.

Origin server 130 can include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of origin server 130 can include software such as an operatingsystem, logs, databases, utilities, drivers, networking software, andother software stored on a computer-readable medium.

Communication links 150-152 each use metal, glass, optical, air, space,or some other material as the transport media. Communication links150-152 can each use various communication protocols, such as wirelesscommunications, cellular communications, Long Term Evolution (LTE), IEEE802.11 (WiFi), Internet Protocol (IP), Ethernet, synchronous opticalnetworking (SONET), hybrid fiber-coax (HFC), circuit-switched,communication signaling, or some other communication format, includingcombinations, improvements, or variations thereof. Communication links150-152 can each be a direct link or can include intermediate networks,systems, or devices, and can include a logical network link transportedover multiple physical links. Although one main link for each of links150-152 is shown in FIG. 1, it should be understood that links 150-152are merely illustrative to show communication modes or access pathways.In other examples, further links can be shown, with portions of thefurther links shared and used for different communication sessions ordifferent content types, among other configurations. Communication links150-152 can each include many different signals sharing the sameassociated link, as represented by the associated lines in FIG. 1,comprising resource blocks, access channels, paging channels,notification channels, forward links, reverse links, usercommunications, communication sessions, overhead communications, carrierfrequencies, other channels, timeslots, spreading codes, transportationports, logical transportation links, network sockets, packets, orcommunication directions.

To further illustrate the operation of a content delivery networkemploying one or more cache nodes, FIG. 3 is presented. FIG. 3 is asystem diagram illustrating communication system 300. Communicationsystem 300 includes content delivery network 310, end user devices330-332, origin servers 340-341, management system 360, and state system380. Content delivery network 310 includes one or more cache nodes (CN)311-313. Each of CN 311-313 can include one or more data storagesystems, such as data storage system 320 of CN 313. End user devices330-332 are representative of a plurality of end user devices which canrequest and receive network content, and any number of end user devices330-332 can be associated with each of content nodes 311-313. CN 311-313and ones of end users 330-332 communicate over associated network links370-372. Content delivery network 310 and origin servers 340-341communicate over associated network links 373-374. Content deliverynetwork 310 and management system 360 communicate over link 375. Contentdelivery network 310 and state system 380 communicate over link 376.Although not shown in FIG. 3 for clarity, each of CN 311-313 can alsocommunicate with each other over one or more network links.

To further illustrate FIG. 3, a brief description of the operation ofcommunication system 300 is included. In operation, end user devices330-332 request network content, such as content 345-346 associated withorigin servers 340-341. Instead of these requests being handled by theindividual origin servers 340-341, individual cache nodes 311-313 ofcontent delivery network 310 receive the content requests over ones oflinks 370-372 and processes the content requests for delivery of thecontent to the associated end user devices 330-332. Requested networkcontent that is already stored in ones of CN 311-313 can be providedquickly to the end user devices, while network content that is notalready stored in ones of CN 311-313 can be responsively requested by anassociated one of CN 311-313 from an appropriate origin server 340-341for delivery by the CN and possible caching by the CN. In this manner,each of CN 311-313 can act as intermediary proxy nodes to provide localand fast access for end user devices 330-332 to network content oforigin servers 340-341 without burdening origin servers 340-341. Forexample, CN 313 includes cached content 321, which can include portionsof any of the content originated at origin servers 340-341.

Data storage system 320 shows exemplary cached content for cache node313, although any of the cache nodes of FIG. 3 can include similarcontent. Each web page is indicated by a native URL, such as a domainname or web address, namely www.alpha.com, www.beta.net, andwww.gamma.gov. Sub-elements of each web page can also have an associatedURL, such as indicated by URL ‘A’-‘C’ in FIG. 3, which can includepathnames, arguments, parameters, query parameters, identities, or otherinformation beyond a domain name or server name.

Data storage system 320 also includes state data 322. State data 322 cancomprise state data for one or more end user devices, and can includeindividualized or shared state data. Data storage system 320 cancomprise geographic locations associated with end user devices, networkaddresses associated with content requests, network addressesoriginating content requests, time/day of content requests, variousinformation about the software environment of end user devices, types ofcontent browser application employed by end user devices to issuecontent requests, versions of the content browser applications,operating system information of the end user devices, and identitiesbrowser plug-in elements associated with content browser applications,among other information. In some examples, state data 322 comprisesstatistical information that spans content requests for many end userdevices, such as counters tracked on a per-URL or per-URI basis. Thestatistical information can be identified by monitoring content requeststo determine the web pages which end users are browsing based in part onthe content requested and header information associated with the contentrequests, such as HTTP referrer field information.

Management system 360 handles configuration changes and statusinformation collection and delivery for system operators and for theorigin server operators or managers. For example, operator device 350can transfer configuration 351 for delivery to management system 360,where configuration 351 can alter the handling of network contentrequests by CN 311-313, among other operations. Also, management system360 can monitor status information for the operation of CN 311-313, suchas operational statistics, and provide this status information as 353 tooperator device 350. Furthermore, operator device 350 can transfercontent 352 for delivery to origin servers 340-341 to include in content345-346. Although one operator device 350 is shown in FIG. 3, it shouldbe understood that this is merely representative and communicationsystem 300 can include many operator devices for receiving statusinformation, providing configuration information, or transferringcontent to origin servers.

State system 380 can include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of state system 380 can include software such as an operatingsystem, logs, databases, utilities, drivers, networking software, andother software stored on a computer-readable medium.

Cache nodes 311-313, origin servers 340-341, management system 360, andstate system 380 can each include communication interfaces, networkinterfaces, processing systems, computer systems, microprocessors,storage systems, storage media, or some other processing devices orsoftware systems, and can be distributed among multiple devices.Examples of CN 311-313, origin servers 340-341, management system 360,and state system 380 can each include software such as an operatingsystem, logs, databases, utilities, drivers, networking software, andother software stored on a computer-readable medium. Content deliverynetwork 310, in addition to including CN 311-313, can include equipmentand links to route communications between CN 311-313 and any of end userdevices 330-332, origin servers 340-341, management system 360, andstate system 380, among other operations.

End user devices 330-332 can each be a user device, subscriberequipment, customer equipment, access terminal, smartphone, personaldigital assistant (PDA), computer, tablet computing device, e-book,Internet appliance, media player, game console, smartwatch, or someother user communication apparatus, including combinations thereof.

Communication links 370-376 each use metal, glass, optical, air, space,or some other material as the transport media. Communication links370-376 can each use various communication protocols, such as wirelesscommunications, cellular communications, IEEE 802.11 (WiFi), Long TermEvolution (LTE), Time Division Multiplex (TDM), asynchronous transfermode (ATM), Internet Protocol (IP), Ethernet, synchronous opticalnetworking (SONET), hybrid fiber-coax (HFC), circuit-switched,communication signaling, or some other communication format, includingcombinations, improvements, or variations thereof. Communication links370-376 can each be a direct link or can include intermediate networks,systems, or devices, and can include a logical network link transportedover multiple physical links. Although one main link for each of links370-376 is shown in FIG. 3, it should be understood that links 370-376are merely illustrative to show communication modes or access pathways.In other examples, further links can be shown, with portions of thefurther links shared and used for different communication sessions ordifferent content types, among other configurations. Communication links370-376 can each include many different signals sharing the sameassociated link, as represented by the associated lines in FIG. 3,comprising resource blocks, access channels, paging channels,notification channels, forward links, reverse links, usercommunications, communication sessions, overhead communications, carrierfrequencies, other channels, timeslots, spreading codes, transportationports, logical transportation links, network sockets, packets, orcommunication directions.

FIG. 4A is a sequence diagram illustrating a method of operatingcommunication system 300, which discusses user state persistence incache nodes. In FIG. 4A, end user device 330 requests a web page fromcache node 311. The web page can comprise various markup language, text,and scripts which reference other content, such as images, videos, text,and the like. This other content can be referenced in the web page usingone or more links or URLs.

Any end user device in FIG. 3 can request network content from any cachenode of content delivery network 310. End user device 330 can follow adomain name lookup process to receive a network address of a particularcache node responsive to a domain name lookup request with a DNS system.This network address can direct content requests for that associateddomain name to a selected cache node, specifically cache node 311 inthis example. Once the network address is obtained, then end user device330 issues a content request for a web resource, such as for a web pageassociated with example domain name www.alpha.com. This content requestcan comprise one or more HTTP GET or POST request methods which arereceived by cache node 311.

In this example, cache node 311 has cached network content associatedwith the requested web page (www.alpha.com) in a data storage system ofcache node 311. This caching can occur responsive to the web pagerequest from end user device 330, a previous request from another enduser device for network content associated with www.alpha.com, or due toa ‘pre-caching’ process which caches predetermined website content priorto end user requests.

Cache node 311 can determine a user state for end user device 330 andpersist the user state on that per-user basis. Cache node 311 can alsodetermine state for more than one of the end user devices, such as totrack request quantities on a per-URL basis or other statisticalinformation for content requests of many end user devices. Cache node311 can process information associated with the content requests, suchas URL information, parameters, query string portions, networkaddresses, or other information included with the content request toidentify various properties of end user device 330. The properties caninclude various information about the requests, such as a networkaddresses of end user devices originating the requests, a location ofend user devices, a time of the content requests, or other properties.Additionally, the properties can include various information about thesoftware environment of end user device 330, such as browser types,application types, operating systems, versioning information, or plug-intypes, among other information. These properties can be included in theuser state for end user device 330.

The state can be processed by cache node 311 to identify a fingerprintor composite identity for end user device 330. This fingerprint caninclude one or more of the properties, metrics, or informationassociated with end user device 330 which can be used to identify futureor further content requests as being associated with end user device330. In some examples, state data comprises statistical information thatspans content requests for many end user devices, such as counterstracked on a per-URL or per-URI basis. The statistical information canbe identified by monitoring content requests to determine the web pageswhich end users are browsing based in part on the content requested andheader information associated with the content requests, such as HTTPreferrer field information.

In a second content request, end user device 330 requests a web pagefrom cache node 311. As before, the web page can comprise various markuplanguage, text, and scripts which reference other content, such asimages, videos, text, and the like. This other content can be referencedin the web page using one or more links or URLs. End user device 330 canfollow a domain name lookup process to receive a network address of aparticular cache node responsive to a domain name lookup request with aDNS system. This network address can direct content requests for thatassociated domain name to a selected cache node, specifically cache node311 in this second example. Once the network address is obtained, thenend user device 330 issues a content request for a web resource, such asfor a web page associated with example domain name www.gamma.gov. Thiscontent request can comprise one or more HTTP GET or POST requestmethods which are received by cache node 311.

In this example, cache node 311 has cached network content associatedwith the requested web page (www.gamma.gov) in a data storage system ofcache node 311. This caching can occur responsive to the web pagerequest from end user device 330, a previous request from another enduser device for network content associated with www.gamma.gov, or due toa ‘pre-caching’ process which caches predetermined website content priorto end user requests.

Cache node 311 can identify the second content request issued by enduser device 330 as being associated with end user device 330. Cache node311 can process the user state or fingerprint associated with the userstate for end user device 330 to identify the second content request asassociated with end user device 330. Based on the content requests anduser state, cache node 311 identifies activity information for end userdevice 330, and deliver the activity information to one or more externalsystems, such as state system 380 which can track activity of end userdevices, such as browsing activity for supplemental content selection,advertisement selection, web analytics, or other purposes. The activityinformation can include an indication of web sites requested by end userdevice 330, a sequence of web sites requested, among other informationwhich can include the user state information. The activity informationcan be anonymized to prevent identification of a user of end user device330 or of user device 330 itself.

Cache node 311 can determine that both web page requests were initiatedby the same end user device. Cache node 311 can identify a sequence ofweb pages for end user device 330, such as which web pages wererequested in which order. Further web page requests can be included inthese determinations which can accumulate statistics and propertiesassociated with end user device 330 or for multiple end user devicesover a period of time. In some examples, these properties andcorrelations between web page requests are transferred for delivery to afurther system, such as state system 380 which can store the propertiesand correlations to perform various analyses and analytics on theproperties from end user device 330 and other end user devices for manyweb page requests and tracking elements. One or more messages can betransferred to state system 380 that indicate the activity informationdetermined by cache node 311 for the various end user activity andproperties. State system 380 can store this tracking information indatabase 381 for later processing, such as data analytics, statisticalprocessing, advertisement selection and monitoring, or page hit ratedetermination, among other web traffic monitoring and analysisprocesses.

Cache node 311 can also transfer the state data and activity informationfor delivery to any of the other cache nodes in content delivery network310. These other cache nodes can then employ the state data or activityinformation to identify when end user device 330 issues further contentrequests at other cache nodes, when end user device has moved to adifferent location, or to correlate activities of many end user devicesamong the various cache nodes. Furthermore, in the examples below, URLshortening can be employed in cache nodes and information related to URLshortening can be exchanged among the cache nodes. Likewise, cache node311 can receive state data and activity information transferred by an ofthe cache nodes of content delivery network 310.

Each cache node can execute functions based on the state data oractivity information which is persisted over more than one contentrequest or web site request of end user devices. These functions can beper-user functions, such as rate limiting of content requests or otherrelated traffic on a per-user basis, statistical monitoring ofindividual users, URL shortening on a per-user basis, accountingtracking, paywall tracking, or other per-user functions. These functionscan include multi-user functions, such as URL shortening, pre-caching ofcontent into a cache node, statistical monitoring, web analyticsmonitoring, rate limiting of content requests or other related trafficon a multi-user basis, or other functions.

At a later time, end user device 330 can receive service from anothercache node, such as cache node 313. In some examples, end user device330 moves to an area serviced by cache node 313, or end user device 330gets routed to cache node 313 instead of cache node 311, such as from anoutage, traffic patterns, packet network routing changes, or otherfactors. When end user device 330 makes further content requests whichare received by cache node 313, cache node 313 can process any receivedstate information, state data, or activity information to conductfurther functions at cache node 313. For example, cache node 313 canidentify the content requests or further traffic issued by end userdevice 330 to identify further activity information for end user device330. This further activity information can include the activityinformation discussed above, among other activity of end user device330. Cache node 313 can also determine state data for end user device330, among other end user devices, which can be used to identifyactivity information. This activity information can be transferred toother cache nodes and for delivery to state system 380.

FIG. 4B is a sequence diagram illustrating another method of operatingcommunication system 300, which discusses per-user function execution incache nodes. In FIG. 4B, end user device 330 requests a web page fromcache node 311. The web page can comprise various markup language, text,and scripts which reference other content, such as images, videos, text,and the like. This other content can be referenced in the web page usingone or more links or URLs.

Any end user device in FIG. 3 can request network content from any cachenode of content delivery network 310. End user device 330 can follow adomain name lookup process to receive a network address of a particularcache node responsive to a domain name lookup request with a DNS system.This network address can direct content requests for that associateddomain name to a selected cache node, specifically cache node 311 inthis example. Once the network address is obtained, then end user device330 issues a content request for a web resource, such as for a web pageassociated with example domain name www.alpha.com. This content requestcan comprise one or more HTTP GET or POST request methods which arereceived by cache node 311.

In this example, cache node 311 has cached network content associatedwith the requested web page (www.alpha.com) in a data storage system ofcache node 311. This caching can occur responsive to the web pagerequest from end user device 330, a previous request from another enduser device for network content associated with www.alpha.com, or due toa ‘pre-caching’ process which caches predetermined website content priorto end user requests.

Cache node 311 determines a user state for end user device 330. Cachenode 311 can process information associated with the content request,such as URL information, parameters, query string portions, networkaddresses, or other information included with the content request toidentify various properties of end user device 330. The properties caninclude various information about the request, such as a network addressof end user device 330 originating the request, a location of end userdevice 330, a time of the content request, or other properties.Additionally, the properties can include various information about thesoftware environment of end user device 330, such as browser types,application types, operating systems, versioning information, or plug-intypes, among other information. These properties can be included in auser state for end user device 330.

Cache node 311 can execute one or more per-user functions based on theproperties identified for end user device 330. The properties can bethose described herein, and can include properties persisted in statedata for end user device 330. The per-user functions can includeactivity tracking functions as discussed in FIGS. 2 and 4A, or can alsoinclude rate limiting of content requests or other related traffic on aper-user basis, statistical monitoring of users, URL shortening on aper-user or multi-user basis, accounting tracking, paywall tracking, orother per-user functions.

Results of the per-user functions can be used by cache node 311 tohandle traffic, content requests, or other processes with respect to enduser device 330. Results can also be transferred for delivery to any ofstate system 380 or other cache nodes in content delivery network 310.In some examples, the results include activity information for end userdevice 330, and cache node 311 can deliver the activity information toone or more external systems, such as state system 380 which can trackactivity of end user devices, such as browsing activity for supplementalcontent selection, advertisement selection, web analytics, or otherpurposes. The result information can include an indication of web sitesrequested by end user device 330, a sequence of web sites requested,among other information which can include the user state information.The result information can be anonymized to prevent identification of auser of end user device 330 or of user device 330 itself.

The per-user functions can include cache node 311 determining that morethan one web page request were initiated by the same end user device.Cache node 311 can identify a sequence of web pages for end user device330, such as which web pages were requested in which order. Further webpage requests can be included in these determinations which canaccumulate statistics and properties associated with end user device 330over a period of time. In some examples, results indicating theseproperties and correlations between web page requests are transferredfor delivery to a further system, such as state system 380 which canstore the properties and correlations to perform various analyses andanalytics on the properties from end user device 330 and other end userdevices for many web page requests and tracking elements. One or moremessages can be transferred to state system 380 that indicate theactivity information determined by cache node 311 for the various enduser activity and properties. State system 380 can store thisinformation in database 381 for later processing, such as dataanalytics, statistical processing, advertisement selection andmonitoring, or page hit rate determination, among other web trafficmonitoring and analysis processes.

Cache node 311 can also transfer the state data and activity informationfor delivery to any of the other cache nodes in content delivery network310, and this state data can include results of per-user functions, orthe per-user functions themselves. These other cache nodes can thenemploy the state data or activity information to execute per-userfunctions when end user device 330 issues further content requests atthe other cache nodes, when end user device has moved to a differentlocation, or to correlate activities of many end user devices among thevarious cache nodes. Furthermore, in the examples below, URL shorteningcan be employed in cache nodes and information related to URL shorteningcan be exchanged among the cache nodes. Likewise, cache node 311 canreceive state data and activity information transferred by an of thecache nodes of content delivery network 310.

Each cache node can execute functions based on the state data oractivity information which is persisted over more than one contentrequest or web site request of end user devices. These functions can beper-user functions, such as rate limiting of content requests or otherrelated traffic on a per-user basis, statistical monitoring ofindividual users, URL shortening on a per-user basis, accountingtracking, paywall tracking, or other per-user functions. These functionscan include multi-user functions, such as URL shortening, pre-caching ofcontent into a cache node, statistical monitoring, web analyticsmonitoring, rate limiting of content requests or other related trafficon a multi-user basis, or other functions.

At a later time, end user device 330 can receive service from anothercache node, such as cache node 313. In some examples, end user device330 moves to an area serviced by cache node 313, or end user device 330gets routed to cache node 313 instead of cache node 311, such as from anoutage, traffic patterns, packet network routing changes, or otherfactors. When end user device 330 makes further content requests whichare received by cache node 313, cache node 313 can process any receivedstate information, state data, per-user functions, per-user functionresults, or activity information to conduct further per-user functionsat cache node 313. For example, cache node 313 can identify the contentrequests or further traffic issued by end user device 330 to identifyfurther activity information for end user device 330. This furtheractivity information can include the activity information discussedabove, among other activity of end user device 330. Cache node 313 canalso determine state data for end user device 330, among other end userdevices, which can be used to identify activity information. Results ofthe per-user functions or information related to activity informationcan be transferred to other cache nodes and for delivery to state system380.

As a further example of the operation of system 300, FIG. 5 ispresented. FIG. 5 is a sequence diagram illustrating a method ofoperating communication system 300. In FIG. 5, a uniform resourcelocator (URL) shortening service is provided by the cache nodes ofcontent delivery network 310. A URL shortening service is one example ofa per-user function executed by any of cache nodes 311-313. As discussedherein, URL shortening typically involves encoding or translating anative URL or natural URL into a shortened or abbreviated form foreasier user by an end user. For example, a URL can include a domainname, server name, pathnames, and query parameters, among otherinformation, and can become very long and cumbersome for an end user touse for linking, transferring, sharing, or other functions. A URLshortening feature can translate the URL for a website or webpage into ashortened version, such as a provided by a URL shortening service.

Cache node 311 can receive a URL shortening request issued by end userdevice 330 to establish a shortened URL for a native URL correspondingto content cached by cache node 311. Responsive to the shorteningrequest, cache node 311 determines a shortened URL corresponding to thenative URL, and indicates the shortened URL to the end user device 330.In this example, end user device 330 issues a URL shortening request forURL ‘A’ associated with a first web site or web page. Cache node 311determines a shortened URL ‘A1’ that corresponds to URL ‘A’ andtransfers this shortened URL ‘A1’ for delivery to end user device 330.

Moreover, cache node 311 can persist shortened URL ‘A1’ in an edge statefor use by the end user device at a later time, or for user by furtherend user devices that issue URL shortening requests for the same nativeURL ‘A’. The relationship between the shortened URL and a native URL canalso be transferred to other cache nodes of content delivery network310, and those cache nodes can use the shortened URL responsive to URLshortening requests issued by end user devices at the other cache nodes.Thus, both the content and the shortened URL can be cached among cachenodes for use by more than one end user or end user device. State system380 can also receive shortened URL, state system can use or track URLsthat are shortened for analytics, statistical monitoring, ad delivery,or other processes.

In a further example, cache node 313 can receive a URL shorteningrequest issued by end user device 332 to establish a shortened URL for anative URL ‘A’. Responsive to the shortening request, cache node 313determines that a shortened URL ‘A1’ has already been determined andreceived from another cache node, namely from cache node 311. Cache node313 can thus transfer shortened URL ‘A1’ for delivery to end user device332 without having to determine a new shortened URL, and thus anenhanced delivery of a shortened URL can be established by contentdelivery network 310.

To further describe the equipment and operation of a cache node, FIG. 6is provided which illustrates cache node 600. Cache node 600 can be anexample of cache nodes 110-111 of FIG. 1 and cache nodes 311-313 of FIG.3, although variations are possible. Cache node 600 includes networkinterface 601 and processing system 610. Processing system 610 includesprocessing circuitry 611, random access memory (RAM) 612, and storage613, although further elements can be included, such as discussed inFIGS. 1 and 3. Example contents of RAM 612 are further detailed in RAMspace 620, and example contents of storage 613 are further detailed instorage system 660.

Processing circuitry 611 can be implemented within a single processingdevice but can also be distributed across multiple processing devices orsub-systems that cooperate in executing program instructions. Examplesof processing circuitry 611 include general purpose central processingunits, microprocessors, application specific processors, and logicdevices, as well as any other type of processing device. In someexamples, processing circuitry 611 includes physically distributedprocessing devices, such as cloud computing systems.

Network interface 601 includes one or more network interfaces forcommunicating over communication networks, such as packet networks, theInternet, and the like. The network interfaces can include one or morelocal or wide area network communication interfaces which cancommunicate over Ethernet or Internet protocol (IP) links. Networkinterface 601 can include network interfaces configured to communicateusing one or more network addresses, which can be associated withdifferent network links. Examples of network interface 601 includenetwork interface card equipment, transceivers, modems, and othercommunication circuitry.

RAM 612 and storage 613 together can comprise a non-transitory datastorage system, although variations are possible. RAM 612 and storage613 can each comprise any storage media readable by processing circuitry611 and capable of storing software. RAM 612 can include volatile andnonvolatile, removable and non-removable media implemented in any methodor technology for storage of information, such as computer readableinstructions, data structures, program modules, or other data. Storage613 can include non-volatile storage media, such as solid state storagemedia, flash memory, phase change memory, magnetic memory, or asillustrated by storage system 460 in this example. RAM 612 and storage613 can each be implemented as a single storage device but can also beimplemented across multiple storage devices or sub-systems. RAM 612 andstorage 613 can each comprise additional elements, such as controllers,capable of communicating with processing circuitry 611.

Software stored on or in RAM 612 or storage 613 can comprise computerprogram instructions, firmware, or some other form of machine-readableprocessing instructions having processes that when executed a processingsystem direct cache node 600 to operate as described herein. Forexample, software drives cache node 600 to receive requests for content,determine if the content is stored in cache node 600, retrieve contentfrom origin servers, transfer content to end user devices, manage datastorage systems for handling and storing the content, determine edgestate information, persist edge state information, and transfer edgestate information to other content nodes, among other operations. Thesoftware can also include user software applications. The software canbe implemented as a single application or as multiple applications. Ingeneral, the software can, when loaded into a processing system andexecuted, transform the processing system from a general-purpose deviceinto a special-purpose device customized as described herein.

RAM space 620 illustrates a detailed view of an example configuration ofRAM 612. It should be understood that different configurations arepossible. RAM space 620 includes applications 630, operating system (OS)640, and content RAM cache 650. Content RAM cache 650 includes RAM spacefor temporary storage of content, such as dynamic random access memory(DRAM).

Applications 630 include content interface 631, configuration interface632, state module 633, per-user function module 634, and content cachingapplication 635. Content caching application 635 handles caching ofcontent and management of storage spaces, such as content RAM cache 650and storage space 665, as well as exchanges content, data, andinstructions via content interface 631, configuration interface 632,state module 633, and per-user function module 634. Content cachingapplication 635 can comprise a custom application, Varnish cachingsoftware, hypertext transfer protocol (HTTP) accelerator software, orother content caching and storage applications, including variation,modifications, and improvements thereof. Applications 630 and OS 640 canreside in RAM space 620 during execution and operation of cache node600, and can reside in system software storage space 662 on storagesystem 660 during a powered-off state, among other locations and states.Applications 630 and OS 640 can be loaded into RAM space 620 during astartup or boot procedure as described for computer operating systemsand applications.

Content interface 631, configuration interface 632, state module 633,and per-user function module 634 each allow a user to interact with andexchange data with content caching application 635. In some examples,each of content interface 631, configuration interface 632, state module633, and per-user function module 634 comprise an applicationprogramming interface (API). Content interface 631 allows for exchangingcontent for caching in cache node 600 by content caching application635, and can also receive instructions to purge or erase data from cachenode 600. Content interface 631 can retrieve tracking elements as wellas network and web page content from origin servers for delivery to endusers. Configuration interface 632 allows for altering the configurationof various operational features of content caching application 635. Insome examples, configuration interface 632 comprises a scriptinglanguage interface, such as Varnish Configuration Language (VCL), Perl,PHP, Javascript, or other scripting or interpreted language-basedinterfaces. State module 633 can log and track requests by end userdevices for various content cached by content node 600, determine stateinformation for the requests and end user devices, persist the stateinformation in state 663, and deliver state or tracking information toexternal systems, among other operations. Per-user function module 634can identify and execute per-user functions or processes based on enduser state information, content requests, or other information. Contentinterface 631, configuration interface 632, state module 633, andper-user function module 634 can each communicate with external systemsvia network interface 601 over any associated network links. In furtherexamples, one or more of elements 631-635 are implemented in VCL or VCLmodules.

Storage system 660 illustrates a detailed view of an exampleconfiguration of storage 613. Storage system 660 can comprise flashmemory such as NAND flash or NOR flash memory, phase change memory,magnetic memory, among other solid state storage technologies. As shownin FIG. 6, storage system 660 includes system software 662, as well ascontent 661, state 663, and per-user functions 664 stored in storagespace 665. As described above, system software 662 can be a non-volatilestorage space for applications 630 and OS 640 during a powered-downstate of cache node 600, among other operating software. Content 661includes cached content, such as the web content examples in FIG. 1,which can include text, data, pictures, video, audio, web pages,scripting, code, dynamic content, or other network content. In thisexample, content 661 includes network content and web pages associatedwith one or more websites, as indicated by www.gamma.gov, www.alpha.com,and www.beta.net. State 663 can comprise URL information, parameters,query string portions, network addresses, or other information includedwith the content requests. State 663 can also comprise networkaddresses, locations of end user devices, time/day of content requests,various information about the software environment of end user devices,such as browser types, application types, operating systems, versioninginformation, or plug-in types, among other information. State 663 can bearranged in one or more data structures and can be arranged on aper-user or multi-user basis. Per-user functions 664 comprise per-userfunctions or processes based on end user state information, contentrequests, or other information. These per-user functions can includerate limiting of content requests or other related traffic on a per-userbasis, statistical monitoring of users, URL shortening on a per-user ormulti-user basis, accounting tracking, paywall tracking, or otherper-user functions.

Cache node 600 is generally intended to represent a discrete ordistributed computing system with which at least software 630 and 640are deployed and executed in order to render or otherwise implement theoperations described herein. However, cache node 600 can also representany computing system on which at least software 630 and 640 can bestaged and from where software 630 and 640 can be distributed,transported, downloaded, or otherwise provided to yet another computingsystem for deployment and execution, or yet additional distribution.

The included descriptions and figures depict specific embodiments toteach those skilled in the art how to make and use the best mode. Forthe purpose of teaching inventive principles, some conventional aspectshave been simplified or omitted. Those skilled in the art willappreciate variations from these embodiments that fall within the scopeof the invention. Those skilled in the art will also appreciate that thefeatures described above can be combined in various ways to formmultiple embodiments. As a result, the invention is not limited to thespecific embodiments described above, but only by the claims and theirequivalents.

What is claimed is:
 1. A method of operating a cache node of a contentdelivery network, the method comprising: caching content from aplurality of origin servers on the cache node; receiving contentrequests from a plurality of end user devices for content; retrievingcontent from an origin server if content requested is not cached in thecache node of the content delivery network; responsively providing thecontent for delivery to the end user devices; processing the contentrequests to determine edge state that corresponds to the contentrequests and persists in the cache node over more than one contentrequest; and transferring information related to the edge state fordelivery to at least one other cache node of the content deliverynetwork for handling of content requests received from one or more ofthe end user devices at the at least one other cache node.
 2. The methodof claim 1, wherein processing the content requests to determine theedge state that corresponds to the content requests comprises storing,in the cache node, metrics associated with at least the content requestsof the end user devices to establish the edge state.
 3. The method ofclaim 2, wherein the metrics comprise at least one of a geographiclocation associated with the end user devices, a network addressassociated with the content requests for the end user devices, a type ofcontent browser application employed by the end user devices to issuethe content requests, a version of the content browser application, andidentities of at least one browser plug-in element associated with thecontent browser application.
 4. The method of claim 1, furthercomprising: determining further content requests received at the cachenode as being associated with ones of the end user devices based on atleast the edge state.
 5. The method of claim 1, further comprising:tracking activity of the end user devices for further content requestsreceived at the cache node based at least on the edge state.
 6. Themethod of claim 1, wherein the content requests are associated withcontent for a first web site, and further comprising: determining thatfurther content requests received by the cache node for content of asecond web site are associated with ones of the end user devices basedon at least the edge state; and identifying browsing statistics for theones of the end user devices comprising a web site browsing sequence forthe ones of the end user devices based at least on the content requestsand the further content requests.
 7. The method of claim 6, furthercomprising: transferring the browsing statistics for delivery to acontent provider associated with at least one of the first web site andthe second web site.
 8. The method of claim 1, further comprising:determining further content requests received at the cache node as beingassociated with at least one of the end user devices based at least onthe edge state; and executing at least one per-user function at thecache node responsive to the further content requests being associatedwith the at least one of the end user devices.
 9. The method of claim 1,further comprising: in the cache node, receiving further informationrelated to the edge state that is transferred by the at least one othercache node, wherein the further information corresponds to activity ofthe end user devices at the at least one other cache node; andincorporating the further information into the edge state for handlingthe content requests received at the cache node for the end userdevices.
 10. A content delivery network comprising a plurality of cachenodes that cache content for delivery to end user devices, the contentdelivery network comprising: a first cache node configured to: receivefirst content requests from an end user device for content cached by thecache node; cache content from a plurality of origin servers in thecontent delivery network; retrieve content from an origin server ifcontent requested is not cached in the first cache node of the contentdelivery network; responsively provide the content for delivery to theend user device; process the first content requests to determine an edgestate that corresponds to the end user device, and persists in the cachenode over more than one content request; transfer information related tothe edge state for delivery to at least a second cache node of thecontent delivery network; and the second cache node configured to:receive second content requests and determine that the second contentrequests are associated with the end user device based at least on theinformation related to the edge state.
 11. The content delivery networkof claim 10, comprising: the first cache node configured to storemetrics associated with at least the first content requests of the enduser device to establish the edge state.
 12. The content deliverynetwork of claim 11, wherein the metrics comprise at least one of ageographic location associated with the end user device, a networkaddress associated with the first content requests, a type of contentbrowser application employed by the end user device to issue the firstcontent requests, a version of the content browser application, andidentities of at least one browser plug-in element associated with thecontent browser application.
 13. The content delivery network of claim10, comprising: the first cache node configured to determine furthercontent requests received at the cache node as being associated with theend user device based on at least the edge state.
 14. The contentdelivery network of claim 10, comprising: the first cache nodeconfigured to track activity of the end user device for further contentrequests received at the cache node based at least on the edge state.15. The content delivery network of claim 10, wherein the first contentrequests are associated with content for a first web site, andcomprising: the first cache node configured to determine that furthercontent requests received by the cache node for content of a second website are associated with the end user device based on at least the edgestate; and the first cache node configured to identify browsingstatistics for the end user device comprising a web site browsingsequence for the end user device based at least on the first contentrequests and the further content requests.
 16. The content deliverynetwork of claim 15, comprising: the first cache node configured totransfer the browsing statistics for delivery to a content providerassociated with at least one of the first web site and the second website.
 17. The content delivery network of claim 10, comprising: thefirst cache node configured to determine further content requestsreceived at the cache node as being associated with the end user devicebased at least on the edge state; and the first cache node configured toexecute at least one per-user function at the cache node responsive tothe further content requests being associated with the end user device.18. The content delivery network of claim 10, comprising: the firstcache node configured to receive further information related to the edgestate that is transferred by the second cache node, wherein the furtherinformation corresponds to activity of the end user device at the secondcache node; and incorporating the further information into the edgestate for handling the content requests received at the first cache nodefor the end user device.
 19. A method of operating a cache node of acontent delivery network that caches content for delivery to end userdevices, the method comprising: in the cache node, caching content froma plurality of origin servers; in the cache node, receiving a contentrequest issued by an end user device; in the cache node, retrievingcontent from an origin server if content requested is not cached in thecache node of the content delivery system; in the cache node,responsively providing the requested content for delivery to the enduser devices; in the cache node, establishing edge state data for theend user device based at least on the content request and properties ofthe end user device; and in the cache node, persisting the edge statedata for handling further content requests from the end user device. 20.The method of claim 19, further comprising: in the cache node, receivingfurther information related to the edge state data that is transferredby at least one other cache node, wherein the further informationcorresponds to activity of the end user device at the at least one othercache node; and incorporating the further information into the edgestate data for handling the content requests received at the cache nodefor the end user device.